This invention relates to optical devices, and more particularly to optical waveguide devices.
In the integrated circuit industry, there is a continuing effort to increase device speed and increase device densities. Optical systems are a technology that promise to increase the speed and current density of the circuits. Optical filters are optical devices that are configured to perform filtering functions. It is known to provide many filtering functions using optical devices. For instance, arrayed waveguide wavelength multiplex an input optical signal into a plurality of output optical signals, each of the output optical signals having its distinct bandwidth that was originally contained in the input optical signal. As such, the arrayed waveguide may be considered as a wavelength filter. Optical deflectors can be discrete elements made from glass or clear plastic, or alternatively can be formed from a semiconductor material, such as silicon.
Optical filters, as with most optical devices, are susceptible to changes in such operating parameters as temperature, device age, device characteristics, contact, pressure, vibration, etc. As such, the optical filters are typically contained in packaging that maintains the conditions under which the optical devices are operating. Providing such packaging is extremely expensive. Even if such packaging is provided, passive optical filters may be exposed to slight condition changes. As such, the passive optical filters perform differently under the different conditions. For example, the filters will filter light differently depending on the conditions. If the characteristics of a passive optical filter is altered outside of very close tolerances, then the optical filter will not adequately perform its function. In other words, there is no adjustability to the passive optical filters.
As such it would be desirable to provide an optical filter that can adjustably filter light to provide a variety of filtering operations. Additionally, it would be desirable to provide a mechanism to compensate in optical filters for variations in the operating conditions.
The present invention is directed to an apparatus and associated method for altering the propagation constant of a region of filtering propagation constant in an optical waveguide. The method comprising positioning an electrode of an electrode shape proximate the waveguide. An altered region of filtering propagation constant is projected into the waveguide that corresponds, in shape, to the electrode shape by applying a voltage to the shaped electrode. The propagation constant of the region of filtering propagation constant is controlled by varying the voltage. Such filter embodiments as an Infinite Impulse Response filter and a Finite Impulse Response filter may be provided.